Elastic fluid turbine



1951 E. G. STERLAND ELASTIC FLUID TURBINE Filed March 10, 1947 9M1 W 2?MM a, 6M MM FIG.

Patented Oct. 30, i951 ELASTIC FLUID TURBINE Ernest George Sterland,Cambridge, England, assignor to The English Electric Company Limited,London, England, a British company Application March 1 0, 1947, SerialNo. 733,663 In Great Britain March 21, 1946 2 Claims (Cl. 253-59) Theinvention relates to elastic fluid (steam or gas) turbines and has theobject of shortening the length of such'turbines required for a givennumber of stages.

It is known in the construction of the rotors of elastic fluid turbinesto machine deep recesses between stages, so as to sub-divide the rotorinto a number of discs each of which has one or more grooves machinedinto its periphery into which the complementarily profiled feet'ofblades may be inserted, which discs are integral with a common centralor hub-like portion of the body. However, the gaps between the stagesincrease the length of the rotor and consequently of the turbine as awhole.

It has also been suggested in the construction of the rotors of suchturbines to divide the rotor into disc-like portions by means of deepannular recesses, the opposing faces of such discs being suitablygrooved near their periphery so that the complementarily profiled feetof blades may be inserted. However, for turbines running at relativelyhigh speeds of revolution in which high stresses are produced in thedisc-shaped portions, it is necessary in order to reduce these stressesto a minimum to shape the faces of the discs in such a way that theaxial width of the discs near the bottom of the annular recess isconsiderably greater than near their periphery. This results in a largeaxial length for each stage of blading, and thus an increased length ofthe rotor and consequently of th turbine as a whole.

It has further been suggested in built-up rotors to arrange the rows ofblades between the individual discs or rings of the rotor assembly, thelowest pressure stage disc only carrying a row of blades in addition tothe interdisc blades of the previous stages.

In order to overcome the disadvantages of these previously suggestedmethods of construction, the following improvement has been made in thefirst method of construction described above, in which according to theinvention deep annular recesses are machined between stages so as tosub-divide the rotor into a number of discs, each integral with thecommon central or hub-like portion of the body, and having one or moregrooves machined in its periphery into which the complementarilyprofiled feet of rows of blades may be inserted. Circular grooves aremachined in the opposing surfaces of at least some of the discs neartheir circumferences, and additional rows of blades, with their rootsprofiled complementarily to said grooves in order to secure fixing, areinserted into the said grooves between such adjacent discs, th rotorblades on the individual discs being arranged substantially on thecentre planes of discs engaged by rotor blades inserted in the profilesbetween adjacent discs on both sides, and being arranged off-set fromthe centre planes of discs engaged on one side only by rotor bladesinserted into the circumferential grooves of adjacent discs, the off-setbeing away from the inserted blades.

In order that it may be more readily understood, the invention isillustrated by way of example in the accompanying drawing, of which:

Fig. 1 is a part of an elevation in section of a turbine according tothe invention, and

Fig. 2 is a detail on a larger scale.

The solid rotor I has a bore 2 for internal inspection of the forgingand is sub-divided into discs 3, 4, 5, 6, by deep annular recesses I, 8,9, machined into the rotor body. Thus these discs are integral with thesolid centre portion adjacent the bore 2 of the rotor I. The blades offour stages ll, I2, I4 and I6 of the turbine are arranged in the usualWay on the discs 3, 4, 5 and 6 respectively, and additional rows ofblades I3 and I 5 are inserted into the gaps between discs 4, 5 and 5, 6respectively. The turbine stator 20 and the guide vanes 2I to 26 for theturbine stages II to I6 are indicated diagrammatically for completenessbut do not in themselves differ from the usual design of suchcomponents.

As will be seen more clearly from Fig. 2, serrations Il are arranged inthe roots of the blades, such as 15, and complementary serrations I8 inthe opposite surfaces of adjacent discs, such as 5 and 6, near theircircumference. The serrations I1 and I8 are interlocked and transmitforces from the turbine blades to the respective discs. Alternatively,the roots of the blades I5 or I3 may be for example T-shaped as shownfor the roots of blades I6, and engage appropriately shaped grooves onthe adjacent discs instead of the serrations shown.

As will be seen from Fig, 1, th turbine blades I2 and I6 are offset fromthe centre planes of their respective discs 4 and 6 towards the sidesaway from the adjacent row of additional inserted blades I3, I5respectively. This is done in order to balance the forces transmittedfrom the blades I3 and E5 to one side of each of the respective discs 4,6. However, in a disc such as 5, having additional blades attached onboth sides, the blades such as I4 are arranged substantially on thecentre line.

The number of inserted stages is shown to be two in Fig. 1 but obviouslyas many such stages can be arranged as required by the overall number ofstages and the particular design of the turbine. In the embodiment shownno such additional blades have been inserted between the stages marked Hand I2 in order that the stresses in the disc 3 which carries the bladesII and whicla fis expose dag higl temperatures, be kept as ,lQw as.possible.) However,' if such considerations do not prevail, a row ofadditional blades could be arranged between stages H and [2 as well.n.i,-. .M.

What I claim as my invention and desire to secure by LettersPatentisgi 1. An elastic fluid turbinegcomrising; a casing, stator bladesarranged in said casing; a rotor T said rows of rotor blades betweenadjacent discs,

the rotor blades on the individual discs being 2 a'rrang'd substantiallyon the centre planes of g I dl scs engaged by rotor blades inserted inthe profil consisting of a central body andudisc s integral with thesaid central body, said disc sloeing fgir; cumferentially grooved onopposing sides near the circumference thereof, rows of rotor -bladesblades "between adjacent discs on both sides, and

foif set from the; centre planes of discs engaged onr one side only by,rotor blades inserted into the lsaid. circumferential grooves ofadjacent discs,

theoiT-set being away from the said inserted

